Really need help with this one, when you get a bike built how do you know what sizes to go for as in stem size 7,8,9,10 cm etc. Any other tips when about to buy a TT bikes very much appreciated.
Go and see someone who is decent at bike fits.
Where do you live ?
Any decent bike shops near you ? What are they ?
And Stems usually get measured in mm not cm
If your getting it built for you then surely that person will need to know your measurements? and therefore know what size you will need.